This invention relates to a tool for use in gravel packing wells. More specifically, the invention relates to a washdown apparatus which can remove wellbore debris by circulating a fluid down the work string and carrying the debris up the casing or by circulating a fluid down the casing, picking up the debris and carrying it up the bore of the assembly and through the work string, so that the wellbore can be cleaned and gravel packed with the same tool, thus reducing the number of trips in the hole to complete the gravel pack operation. The term xe2x80x9cgravel packxe2x80x9d may mean high rate, water rate, frac pac, or other stimulation operation involving placement of sand or synthetic proppant in the target formation/casing annulus.
In wells in geologic formations where the production of sand from the formation along with liquids and gases being produced therefrom is a problem, it is well known in the art to install a production screen in the production tubing and pack gravel around the screen to prevent the sand from the formation flowing in the production tubing. Hereinafter xe2x80x9cwell screenxe2x80x9d or xe2x80x9cproduction screenxe2x80x9d means any well filtration device intended to inhibit the flow of sand, or other fines into the production tubing, such as a screen, slotted liner, perforated pipe or sintered metal tube.
In such an arrangement a gravel pack screen assembly is run into the formation on a string of tubing to the desired location and a slurry containing gravel, which is typically gravel sand or proppant mixed in water or a gelled liquid, is pumped down to the exterior of the gravel pack screen assembly to fill the area between the screen assembly and the producing formation. After a sufficient amount of gravel has been pumped down to the exterior of the gravel pack screen assembly to completely fill he area between the screen assembly and the producing formation, the service tool is removed from the well and production tubing is installed.
Very often a wellbore will have debris that must be removed prior to completing the gravel pack operation. Such debris, if not removed, can cause the gravel packing process to be temporarily aborted. In other words, if the debris remains in the wellbore, the gravel pack assembly would have to be removed and the debris circulated out of the well with a different tool prior to the completion of the gravel pack process. Influx of formation debris can occur during necessary pipe trips, which would again necessitate cleaning of the wellbore before the gravel pack assembly was installed. Typically, to avoid such problems, fluid is circulated down a work string and up through the annulus between the work string and the wellbore until the wellbore is sufficiently free from debris so that the gravel packing operation can be performed. The work string is then removed and the gravel pack assembly is lowered into the wellbore.
The foregoing difficulties are eliminated according to a preferred embodiment of the present invention by a universal washdown system, or apparatus, which can be used both to circulate fluid through a wellbore to clean debris therefrom and can be used to gravel pack a production zone. The system comprises a production assembly and a multi-position service tool assembly disposed in the production assembly. An annulus is defined between the side of the wellbore and the production assembly. The production assembly may include a packer for sealingly engaging the wellbore and for suspending the production assembly therein, and a liner assembly having a longitudinal liner bore defined therethrough extending downward from the packer. The multi-position service tool assembly is releasably attached to the packer and sealingly engages a packer bore defined in the packer. The service tool has a longitudinal central flow passage extending therethrough. At least one crossover port, and preferably a plurality of crossover ports are defined through a side of the service tool and intersect the longitudinal central flow passage.
The multi-position service tool assembly is movable from a first position to a second position in the production assembly. When the washdown apparatus is lowered into the well, the service tool is releasably connected to the production assembly in the first position. The crossover ports are sealingly engaged by the liner when the tool is in the first position so that no flow is allowed therethrough. The central flow passage is communicated with the wellbore through a lower end of the production assembly. Thus, fluid flowing down the central flow passage will exit the production assembly at a lower end thereof and will pass into the wellbore. Likewise, fluid can be displaced down the annulus between the production assembly and the wellbore as the apparatus is being lowered into the wellbore. The fluid will enter the lower end of the production assembly and pass upward through the longitudinal central flow passage of the service tool assembly into the work string thereabove until it reaches the surface.
The service tool is slidable in the production assembly from the first position to the second position by pulling longitudinally thereon. Flow ports defined in the liner assembly are located above the crossover port when the service tool is in the first position. When the tool is in the second position, the crossover port is communicated with the flow ports defined through the liner. Thus, when the service tool assembly is in the second position, fluid passing down through the central flow passage can pass through the crossover port and the flow ports in the liner so that the central flow passage is communicated therethrough with the annulus defined between the liner assembly and the wellbore.
The apparatus further includes tool retaining means for retaining the service tool in the second position. The apparatus is run into the well in the first position so that fluid can be circulated through the longitudinal central flow passage and the annulus between the apparatus and the wellbore to clean out any debris in the wellbore. Once the wellbore has been cleaned, a production screen connected in the liner assembly is positioned adjacent a production zone and the packer is set. The service tool is then pulled upward into the second position and is retained in the second position by the tool retaining means.
A wash shoe may be attached to a lower end of the production assembly. The wash shoe may include an outer shoe housing attached to the liner assembly below the production screen. An inner sleeve is slidably disposed in and releasably attached to the outer shoe housing. The inner sleeve has a bore communicated with the central flow passage and has a plurality of ports defined therethrough. When the service tool is in the first position, the ports in the inner sleeve communicate the longitudinal central flow passage with a lower exit opening defined on the outer shoe housing. The lower exit opening comprises the lower end of the production assembly. A wash pipe stinger disposed at the lower end of the service tool is releasably connected to the inner sleeve. When the service tool assembly is pulled longitudinally from the first position to the second position, the inner sleeve of the wash shoe is pulled longitudinally to a closed, or sealed position. In the closed position, the inner sleeve seals against the outer shoe housing, so that the ports defined therethrough are blocked and no communication is allowed through the lower end of the production assembly. The wash pipe stinger is releasably attached to the inner sleeve so that as the service tool assembly is pulled longitudinally, the wash pipe stinger will detach from the inner sleeve. The shoe includes a shoe retaining means for retaining the inner sleeve in the sealed position. Thus the inner sleeve may be positively locked so it cannot slide downward back into the open position. When the service tool assembly is in the second position, the lower end of the wash pipe stinger is preferably adjacent the production screen.
The invention also includes a multi-piece drop dart which comprises a setting means for setting the packer and a sealing means for sealing the central flow passage to prevent downward flow therethrough below the crossover port. The multi-piece drop dart has an outer setting sleeve that will engage an opening sleeve disposed in the service tool assembly. As fluid pressure is applied through the longitudinal central flow passage, the setting sleeve will cause the opening sleeve to slide downward. When the opening sleeve slides downward, the central flow passage will be communicated with a piston that will hydraulically set the packer. The multi-piece drop dart further includes a sealing dart releasably attached to the outer setting sleeve. Increased fluid pressure will cause the sealing dart to be detached from the outer setting sleeve. The sealing dart will pass downward through the central flow passage and will engage a crossover seat defined in the service tool assembly below the crossover port. The sealing dart will prevent downward flow through the central flow passage below the crossover port. Finally, as fluid pressure increases, a closing ball, which is releasably connected to the sealing dart, will detach and will engage a ball seat disposed in the service tool below the crossover seat.
Once the packer has been set, the service tool can be pulled upward into the second position, which will move the wash shoe into the closed position, and a gravel pack fluid can be displaced down the central flow passage. Because the sealing dart has engaged the crossover seat, the gravel pack fluid will pass through the crossover ports in the service tool and the flow ports defined in the liner assembly. The gravel pack fluid will pass downward in the annulus between the production assembly and the wellbore. The gravel pack fluid will continue to be displaced until a sufficient amount of gravel or proppant is placed in the formation and around the production screen. The liquid used to displace the gravel can pass into the formation, and is also communicated with the central flow passage through the production screen and the wash pipe stinger which is preferably positioned adjacent the production screen when the service tool assembly is in the second position.